1. Field of the Invention
The present invention relates to a liquid crystal projector, and more particularly, to an optical system for a liquid crystal projector enabling to minimize a size of the optical system and a count of optical parts constructing the optical system using three pieces of reflective type liquid crystal displays.
2. Background of the Related Art
Lately, a projector, which magnifies and projects a small image to a large screen, attracts attention as a flat display enabling to realize a large-sized screen with a slim design instead of a cathode ray tube having a large volume and a limited screen size. The projector as a display constructing a small screen image uses a cathode ray tube or a liquid crystal display(hereinafter abbreviated LCD), and particularly, a liquid crystal projector using LCD prevails for the trend of slim size. The liquid crystal projector generally uses a backlit or reflective LCD. Such a liquid crystal display has been developed on the basis of small size, lightness, and high brightness, while an LCD panel has been developed on the basis of high opening ratio and high resolution. In order to cope with the trends of the liquid crystal projector such as high resolution, small size, and low price, a reflective type LCD panel is widely used for the liquid crystal projector.
The liquid crystal projector realizes an image on an LCD panel using light emitted from a light source and images a video pf the LCD panel on a screen using a projecting optical system, whereby the video imaged on the screen is appreciated. When the projector is constructed in a manner that the image of the LCD panel is directly projected to a rear screen, a projection distance between the screen and the projecting optical system should be provided so that a sufficient space behind the screen is essential. Hence, the projector becomes thickened so as to make it difficult to reduce the volume of the projector. In order to settle such a problem, a total reflection mirror is inserted between the screen and projecting optical system so as to fold a light path. Thus, a thickness of the projector is reduced. Although it is also able to reduce the thickness of the projector further by decreasing an arranged angle of the total reflection mirror, there is a limit to reduce the arranged angle of the total reflection mirror and the projecting optical system so as to project the image on the rear screen without distortion. Besides, there is a limitation to reducing the thickness of the optical system including an illumination system, LCD, and a projecting lens system due to the natural span length of the system itself.
FIG. 1 illustrates a diagram of an optical system for a liquid crystal projector according to a related art.
Referring to FIG. 1, a liquid crystal projector according to a related art includes first and second fly eye lenses (hereinafter abbreviated FEL) 6 and 8 arranged between a light source 4 and a total reflection mirror 14, a polarizing beam split array(hereinafter abbreviated PBS array) 10, a first light-concentrating lens 12, and a second light-concentrating lens 16 arranged between the total reflection mirror 14 and a first dichroic mirror 18. A white light irradiated from a lamp of the light source 4 is reflected by an elliptical mirror so as to proceed toward the first FEL 6. The first FEL 6 divides the incident light into cell units so as to be focused on the respective lens cells of the second FEL 8. The second FEL 6 transforms the incident light into the parallel light in parallel with a specific part so as to transmit toward the PBS array. The PBS array 10 separates the incident light into linear polarized lights having specific optical axes respectively, i.e. a P polarized light and an S polarized light, and a xc2xd wavelength plate(not shown in the drawing) attached to a rear of the PBS array 10 in part transforms the transmitted P polarized light into the S polarized light. Hence, the incident light is entirely transformed into the S polarized light by the PBS array 10 so that the light irradiated from the light source 4 becomes incident on liquid crystal panels 26R, 26G, and 26B mostly. The first light-concentrating lens 12 concentrates the incident light from the PBS array 10 on the total reflection mirror 14, and the total reflection mirror 14 totally reflects the incident light from the first light-concentrating lens 12 so as to make the reflected light proceed toward the second light-concentrating lens 16. The second light-concentrating lens 16 concentrates the incident light from the total reflection mirror 14 upon the first dichroic mirror 18. The first dichroic mirror 18 transmits a blue area of the incident light as well as reflects green and red areas of the incident light of which wavelengths are longer than that of the blue light.
The optical system for the liquid crystal projector includes a second dichroic mirror 20 arranged between the first dichroic mirror 18 and the red liquid crystal panel 26R, a first polarizing film 22R, a first polarizing beam split prism (hereinafter abbreviated PBSP) 24R, a second polarizing film 22G and a second PBSP 24G arranged between the second dichroic mirror 20 and the green liquid crystal panel 26G, a first relay lens 27 arranged between the first dichroic mirror 18 and the blue liquid crystal panel 26B, a second total reflection lens 28, a second relay lens 29, a third polarizing film 22B, a third PBSP 24B, a dichroic prism 30 arranged between the first to third PBSPs 24R, 24G, and 24B, and a projecting lens 32 installed to confront a light-projecting surface of the dichroic prism 30. The second dichroic mirror 20 reflects a green region light of the incident light reflected on the first dichroic mirror 18 so as to make the reflected green region light proceed toward the second polarizing film 22G and transmits a red region light to proceed toward the first polarizing film 22R. The second total reflection mirror 28 reflects an incident blue region light transmitted through the first dichroic mirror 18 to proceed toward the third polarizing film 22B. In this case, the first and second relay lens 27 and 29 as field lenses relay an imaging point of the blue region light so as to make the imaging point re-imaged on the blue liquid crystal panel 26B. The first to third polarizing films 22R, 22G, and 22B transmit just the S polarized lights in parallel with the corresponding optical axes of the polarizing films to make the S polarized lights proceed to the first to third PBSPs 24R, 24G, and 24B, respectively. The first to third PBSPs 24R, 24G, and 24B reflect the red, green, and blue S polarized lights, which are transmitted through the first to third polarized films 22R, 22G, and 22B and then become incident, to proceed toward the red, green, and blue liquid crystal panels 26R, 26G, and 26B, respectively. Moreover, the first to third PBSPs 24R, 24G, and 24B acquires image information from the red, green, and blue liquid crystal panels 26R, 26G, and 26B respectively so as to transmit the red, green, and blue lights transformed into the P polarized lights to proceed toward the dichroic prism 30. The red, green, and blue liquid crystal panels 26R, 26G, and 26B as reflective type liquid crystal panels transform the incident S polarized lights reflected upon the first to third PBSPs 24R, 24G, and 24B into the P polarized lights respectively in accordance with the image signal, thereby realizing an image. The dichroic prism 30 composes the incident red, green, and blue lights by acquiring the image information form the red, green, and blue liquid crystal panels 26R, 26G, and 26B respectively so as to project the composed light through the projecting surface toward the projecting lens 32. First and second polarizing transform films(not shown in the drawing) are arranged between the first and third PBSPs 24R and 24B and the dichroic prism 30, respectively, so as to transform the P polarized lights into the S polarized lights. Hence, the dichroic prism 30 reflects red and blue lights of the S polarized light component incident through the first and second polarizing transform films toward the projecting lens 32 as well as transmits the green light of the P polarized light component incident through the second PBSP 24G toward the projecting lens 32, thereby composing an image of red, green, and blue lights. The projecting lens 32 magnifies to project the image incident from the dichroic prism 30 on a screen.
The above-constructed liquid crystal projector according to the related art uses three pieces of liquid crystal panels, thereby requiring a plurality of dichroic mirrors to separate a whit light from a light source into red, green, and blue lights. Moreover, the liquid crystal projector according to the related art uses the reflective type liquid crystal panels, thereby requiring a plurality of polarizing beam split prisms making different paths of the incident/projected lights by taking the reflective type liquid crystal panel as a reference. The optical system for such a liquid crystal projector using three pieces of the reflective liquid crystal panels according to the related art requires excessive optical parts so as to increase a size of the optical system. Therefore, there is a limitation to reducing a thickness of the system proportional to the span length of the optical system, thereby having difficulty in providing a slim size.
In order to decrease the span length of the optical system, lately proposed is an optical system having a double-layered structure that a color separating part is formed on a color composing part and a projecting lens system. Unfortunately, such a double-layered optical system uses an excessive number of optical parts, thereby having difficulty in reducing a size of the optical system.
Accordingly, the present invention is directed to an optical system for a liquid crystal projector that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an optical system for a liquid crystal projector reducing a number of optical parts as well as a size of the optical system.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, in an optical system for a liquid crystal projector composing monochromatic images realized in first to third reflective liquid crystal panels respectively for enlarging projection of the composed images, the optical system according to the present invention includes a light source emitting a white light, an illumination part transforming the white light into a predetermined linearly-polarized light and releasing the linearly-polarized light, a first color select transforming to polarize the linearly-polarized light released from the illumination part into another linearly-polarized light in accordance with a wavelength region, and a color resolution/composition part splitting an incident light from the first color select in colors to be incident on the first to third reflective liquid crystal panels respectively and composing the light of which image information is acquired from the first to third liquid crystal panels to release the composed light to a projecting lens system for the enlarging projection, wherein the first to third liquid crystal panels are arranged to confront first to third faces of the color resolution/composition part in part, wherein the projecting lens system is arranged to confront a fourth face of the color resolution/composition part in part, and wherein the first color select is arranged to confront another portion of the same face of the third liquid crystal panel.
Preferably, the color resolution/composition part comprises first to fourth same-sized blocks bonded one another.
Preferably, the first to fourth blocks are bonded to each other using UV rays. More preferably, each of the first to fourth blocks has a triangular cylindrical figure.
Preferably, the color resolution/composition part includes a first dichroic coating face coated on a contact face between the first and second blocks to separate a first color light from the incident light from the first color select, a first polarizing beam split coating face coated on a contact face between the second and third blocks to split a transmitted light from the first dichroic coating face into second and third color lights by polarization so as to make the second and third color lights incident on the first and second liquid crystal panels, respectively, the first polarizing beam split coating face making the polarized second and third color lights proceed to the projecting lens system by acquiring image information from the first and second liquid crystal panels, a second polarizing beam split coating face coated on a contact face between the first and fourth blocks to reflect the first color light from the first dichroic coating face to become incident on the third liquid crystal panel, the second polarizing beam split coating face transmitting the first color light of which image information is acquired from the third liquid crystal panel, and a second dichroic coating face coated on a contact face between the third and fourth blocks so as to transmit the second and third color lights from the first polarizing beam split coating face to the projecting lens system, the second dichroic coating face reflecting the first color light from the second polarizing beam split coating face to the projecting lens system.
More preferably, the first and second dichroic coating faces reflect a blue light and transmit green and red lights, and the first and second polarizing beam split coating faces reflect an S-polarized light and transmits a P-polarized light.
Preferably, the color resolution/composition part further includes first and second anti-reflection coating faces coated on faces confronting the first color select and the projecting lens system respectively to prevent reflective lights, respectively.
Preferably, the color resolution/composition part includes color-transmitting dichroic coating faces coated on faces confronting the first to third liquid crystal panels respectively to transmit the color lights of the corresponding wavelength regions, respectively.
Preferably, the optical system further includes a second color select transforming the lights proceeding between the color resolution/composition part and the projecting lens system into a P-polarized light when a P-polarizing screen transmitting the P-polarized light only is used as a screen on which a composed image enlarged/projected by the projecting lens system is imaged.
More preferably, the first and second color selects transforms a green light by polarization and transmits other lights of rest wavelengths intact, the first color select transforms a green S-polarized light into a P-polarized light and transmits red and blue S-polarized lights intact, and the second color select transforms a green S-polarized light into a P-polarized light and transmits red and blue P-polarized lights intact.
In another aspect of the present invention, in an optical system for a liquid crystal projector composing monochromatic images realized in first to third reflective liquid crystal panels respectively for enlarging projection of the composed images, the optical system includes a light source emitting a white light, an illumination part transforming the white light into a predetermined linearly-polarized light and releasing the linearly-polarized light, a first color select transforming to polarize the linearly-polarized light released from the illumination part into another linearly-polarized light in accordance with a wavelength region, a color resolution/composition part constructed with first to fourth blocks bonded each other and having the same size, the color resolution/composition part splitting an incident light from the first color select in colors to be incident on the first to third reflective liquid crystal panels respectively and composing to release the light of which image information is acquired from the first to third liquid crystal panels, and a second color select transforming the green light of the linearly-polarized lights released from the color resolution/composition part by polarization and transmitting the rest of the lights having other wavelengths so as to release the lights to the projecting lens system for the enlarging projection, wherein the first to third liquid crystal panels are arranged to confront first to third faces of the color resolution/composition part in part, wherein the projecting lens system is arranged to confront a fourth face of the color resolution/composition part in part, and wherein the first color select is arranged to confront another portion of the same face of the third liquid crystal panel.
Preferably, the color resolution/composition part includes a first dichroic coating face coated on a contact face between the first and second blocks to separate a blue color light from the incident light from the first color select, a first polarizing beam split coating face coated on a contact face between the second and third blocks to split a transmitted light from the first dichroic coating face into red and green color lights by polarization so as to make the red and green color lights incident on the first and second liquid crystal panels, respectively, the first polarizing beam split coating face transmitting and reflecting the polarized red and green color lights by acquiring image information from the first and second liquid crystal panels, a second polarizing beam split coating face coated on a contact face between the first and fourth blocks to reflect the blue color light from the first dichroic coating face to become incident on the third liquid crystal panel, the second polarizing beam split coating face transmitting the blue color light of which image information is acquired from the third liquid crystal panel, and a second dichroic coating face coated on a contact face between the third and fourth blocks so as to transmit the red and green color lights transmitted/reflected through/from the first polarizing beam split coating face to the second color select, the second dichroic coating face reflecting the blue color light transmitted through the second polarizing beam split coating face to the second color select.
Preferably, the first and second dichroic coating faces reflect the blue color light and transmit the green and red color lights.
More preferably, the first and second polarizing beam split coating faces reflect an S-polarized light and transmits a P-polarized light.
Preferably, the color resolution/composition part further comprising first and second anti-reflection coating faces coated on faces confronting the first color select and the projecting lens system respectively to prevent reflective lights.
Preferably, the color resolution/composition part further includes color-transmitting dichroic coating faces coated on faces confronting the first to third liquid crystal panels respectively to transmit the color lights of the corresponding wavelength regions, respectively.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.